Fig. 158.—Histiopterus recurvirostris.
Gerres.—Body oblong, or rather elevated, covered with scales of moderate size, which are either entirely smooth or minutely ciliated. Mouth very protractile, and descending when thrust out. Eye rather large. No canine teeth; dentition feeble, and palate toothless. The two divisions of the dorsal fin are nearly separated by a deep incision. Formula of the vertical fins—D. 9/10 A. 2·3/7·9. Caudal fin forked. Præoperculum generally without denticulation. Lower pharyngeal bones coalescent.
Fig. 159.—Gerres altispinis, from the mouth of the Ganges.
More than thirty species are known of this genus, which bear so close a resemblance to one another that their distinction is rather difficult. They live in the seas between the Tropics, and some, perhaps all, of the species enter fresh water. Very rarely they exceed a length of ten inches; nearly all have a plain silvery coloration. The coalescence of their lower pharyngeals renders their systematic position rather uncertain, and, indeed, some Ichthyologists have referred them to the Pharyngognaths.
Scolopsis.—Body oblong, covered with scales finely serrated and of moderate size. Jaws nearly equal in length anteriorly; cleft of the mouth horizontal. Teeth villiform, without canines; palate toothless. One dorsal fin. Formula of the vertical fins: D. 10/9 A. 3/7. Caudal fin forked. Præoperculum distinctly denticulated; infraorbital ring with a spine directed backwards. Branchiostegals, five.
Fig. 160.—Infraorbital spine of Scolopsis monogramma.
Marine, and of small size. Twenty-five species are known from the tropical parts of the Indo-Pacific. Heterognathodon is an allied genus, but without the infraorbital spine.